Analysis of Negative Revisions to Natural Gas Reserves in Texas

Early problems in overestimating effective porosity in some deep Delaware Basin carbonate reservoirs in the Permian Basin, particularly in District 8, resulted in noticeable negative revisions once these issues were resolved. However, the net negative volume of revisions for the Permian Basin (Districts 8, SA, and parts of 7B and 7C) was nearly an order of magnitude less than that for the Gulf Coast Basin. The largest negative revisions of total natural gas reserves were concentrated in the Gulf Coast within Texas Railroad Commission Districts 2, 3, and 4. District 4, with the largest volume of negative revisions, accounted for 56 percent of all negative revisions in Texas for the period 1966-1979. The total for the three districts equaled that of the whole state for the same period. Negative revisions of non-associated gas reserves in Districts 2, 3, and 4 accounted for more than two-thirds of the total gas negative revisions for the entire state from 1966 through 1979. Large negative revisions were mainly due to a combination of interrelated factors. Among these, the original overestimation of natural gas reserves in the Texas Gulf Coast, fueled by optimism from market-related incentives, was significant. These estimates underwent insufficient critical review and reassessment, as supplies greatly exceeded demand. Continued high Reserves to Production (R/P) ratios into the 1960s further delayed reassessment. Technical variables such as water saturation, reservoir heterogeneity, and recovery factors, as well as non-technical variables including economic climate and regulatory controls, were analyzed. Concern should be raised regarding the quality of reserve estimates declared during times of excess supply, as these reserves would not have undergone the test of extended maximum demand. However, there have been more frequent reviews of actual recoverable reserves over the last five years. Continued careful review of technical factors and awareness of the impacts of economic and regulatory environment changes suggest that extensive negative revisions over the next 10 to 20 years can be avoided.Bureau of Economic Geolog

Update of Atlas of Major Texas Oil Reservoirs Data Base and Atlas of Major Texas Gas Reservoirs Data Base

Updating both the "Atlas of Major Texas Oil Reservoirs: Database" (Holtz and others, 1991) and the "Atlas of Major Texas Gas Reservoirs: Database" (Garrett and others, 1991) centered on updating cumulative production data current to December 31, 1992, for reservoirs already in the database and adding new significant-sized reservoirs (cumulative production greater than 1 million barrels of oil equivalent) to the databases. Addition of new reservoirs to the database resulted in the modification of existing plays or the determination of new plays. Play boundaries were also modified to accommodate the additional reservoirs. Oil and gas production data used for the cumulative production update and the determination of significant-sized reservoirs were obtained from Dwight's Energy data. For reservoirs already included in the Atlas databases, annual production values were added to the cumulative production already determined by the Bureau of Economic Geology (BEG) or reported by the Railroad Commission of Texas. For new reservoirs, the cumulative production values reported by Dwight's Energy data were applied. Oil reservoirs originally listed in both databases because of large gas production were combined and now are listed only in the updated Oil Atlas database.Bureau of Economic Geolog

Geologic Anaylsis of Primary and Secondary Tight Gas Sand Objectives Phase A&B

Finley (1982) listed geologic and engineering characteristics of over 30 blanket-geometry tight gas sandstones in a survey of 16 sedimentary basins. Emphasis was placed on defining elastic depositional systems and on using constituent facies as a method of evaluating the common features of stratigraphic units of different ages in diverse sedimentary and structural settings. Blanket-geometry tight gas sandstones considered suitable for future research by the Gas Research Institute were found to occur primarily within deltaic and barrier-strandplain depositional systems. An assessment of expected transferability of research results (extrapolation potential) was made between stratigraphic units, and more detailed study of six formations was recommended. The Corcoran and Cozzette Sandstones of the Piceance Creek Basin and the Travis Peak Formation of the East Texas Basin and North Louisiana Salt Basin were recommended for research by the Gas Research Institute on blanket-geometry tight gas sandstones, and initial studies of depositional systems were begun. The Corcoran and Cozzette represent the barrier-strandplain system and contain barrier, offshore bar, and associated marginal-marine facies. Detailed studies of the Corcoran-Cozzette in Shire Gulch and Plateau Fields show shoreface sequences common to the lower parts of both units, and bay-lagoon and deltaic facies occur in the upper parts. The Travis Peak Formation represents a deltaic system, having a lower subdivision of progradational deltaic facies, a thick middle subdivision of braided alluvial deposits, and an upper subdivision of marginal marine deposits influenced by marine transgression. Sands greater than 50 ft thick are prominent in the middle subdivision in areas on the west flank of the Sabine Uplift. The Frontier Formation and the upper Almond Formation of the Greater Green River Basin and the Olmos Formation of the Maverick Basin are not recommended for further research, but should be considered when the need arises to test barrier, offshore bar, and possibly deltaic facies outside the two main research areas. The estimated gas resources associated with the Corcoran-Cozzette and the Travis Peak in Texas are 3.7 and 17.3 Tcf respectively. The Mancos "B" of the Piceance Creek Basin is not recommended for any additional research because its unique distribution of lithologies limits its extrapolation to a small group of shelf deposits, some of which have already been investigated. The extrapolation potential of the Travis Peak is largely to itself over a wide area of East Texas and North Louisiana. Extrapolation potential of the Corcoran and Cozzette extends to a large number of stratigraphic units, mostly within the Upper Cretaceous of the Rocky Mountain Region.Bureau of Economic Geolog

Salinity Variations and Chemical Compositions of Waters in the Frio Formation, Texas Gulf Coast

Waters produced from sandstone reservoirs of the deep Frio Formation exhibit spatial variations in chemical composition that roughly coincide with the major tectonic elements (Houston and Rio Grande Embayments, San Marcos Arch) and corresponding depositional systems (Houston and Norias deltas, Greta-Carancahua barrier/strandplain system) that were respectively active along the upper, lower, and middle Texas Coast during Frio deposition. Waters of the upper coast typically have relatively high salinities (maximum total dissolved solids >80,000 mg/L), high calcium (200 to 9,000 mg/L), high sodium (>15,000 µg/L), relatively high potassium (>150 mg/L), low to moderate Cl/Na ratios (1.4 to 1.9), and high Cl/Br ratios (>400). When compared with adjacent areas of Frio production, waters of the middle coast have lower salinities (maximum total dissolved solids 80,000 mg/L, extremely high calcium (1,800 to 34,000 mg/L), high sodium (>15,000 mg/L), high potassium (>150), extremely high Cl/Na ratios (>2), and low Cl/Br ratios (<250). Calcium concentrations actually exceed sodium concentrations in some South Texas waters.Bureau of Economic Geolog

Analysis of Negative Revisions to Natural Gas Reserves in Texas

The role of negative revisions in the large-scale decline in natural gas reserves in Texas during the late 1960s and through the 1970s was examined. Analysis of the factors that contributed to the negative revisions determined that no single element was responsible. However, (1) continued high levels of production, (2) original optimistic estimates of gas in place and recovery factors, (3) market-related factors that encouraged overestimation of reserves, and (4) unusually high reserves-to-production ratios (> 15) that obscured the underlying weakness in reserves combined in the Texas Gulf Coast to drastically reduce booked reserves of natural gas. Negative revisions totaling more than 20 trillion cubic feet during the period were found to have resulted mainly from ambiguities in the degree of reservoir heterogeneity, in calculation of water saturations, and in drive mechanism, along with the overestimation of reserves due to optimism encouraged by market-related incentives. The much-reduced reserves-to-production ratios that now exist, along with continued closer monitoring of technical, economic, and regulatory factors that affect gas reserves, indicate that a return of extensive negative revisions over the next 10 to 20 years is avoidable.Bureau of Economic Geolog

Opportunities for Additional Recovery in University Lands Reservoirs -- Characterization of University Lands Reservoirs, Final Report

In 1984, The University of Texas System funded a Bureau of Economic Geology project, "Characterization of University Lands Reservoirs," to assess in detail the potential for incremental recovery of oil from University Lands reservoirs by extended conventional methods. The objectives of the 5-year project were to quantify the volumes of unrecovered mobile oil remaining in reservoirs on University Lands, to determine whether the specific location of the unrecovered mobile oil could be delineated through integrated geoscience characterization of individual reservoirs, and to develop strategies to optimize recovery of this resource. Unrecovered mobile oil is mobile at reservoir conditions but is prevented from migrating to the wellbore by geologic complexities or heterogeneities. This final report describes results of the 5 years of research conducted on University Lands reservoirs. One hundred and one reservoirs, each of which has produced more than 1 million stock tank barrels (MMSTB) of oil, were included in a resource assessment and play analysis undertaken (1) to determine the volumes and distribution of all components of the University Lands resource base and (2) to select reservoirs for detailed analysis. These reservoirs collectively contained 7.25 billion barrels (BSTB) of oil at discovery, have produced 1.5 BSTB, and contain 200 MMSTB of reserves. Ultimate recovery at implemented technology is projected to be 24 percent of the original oil in place; thus, 5.5 BSTB of oil will remain after recovery of existing reserves. Unrecovered mobile oil (exclusive of reserves) amounts to 2.2 BSTB, and immobile, or residual, oil totals 3.3 BSTB.Bureau of Economic Geolog

Psychological interventions in asthma

Asthma is a multifactorial chronic respiratory disease characterised by recurrent episodes of airway obstruction. The current management of asthma focuses principally on pharmacological treatments, which have a strong evidence base underlying their use. However, in clinical practice, poor symptom control remains a common problem for patients with asthma. Living with asthma has been linked with psychological co-morbidity including anxiety, depression, panic attacks and behavioural factors such as poor adherence and suboptimal self-management. Psychological disorders have a higher-than-expected prevalence in patients with difficult-to-control asthma. As psychological considerations play an important role in the management of people with asthma, it is not surprising that many psychological therapies have been applied in the management of asthma. There are case reports which support their use as an adjunct to pharmacological therapy in selected individuals, and in some clinical trials, benefit is demonstrated, but the evidence is not consistent. When findings are quantitatively synthesised in meta-analyses, no firm conclusions are able to be drawn and no guidelines recommend psychological interventions. These inconsistencies in findings may in part be due to poor study design, the combining of results of studies using different interventions and the diversity of ways patient benefit is assessed. Despite this weak evidence base, the rationale for psychological therapies is plausible, and this therapeutic modality is appealing to both patients and their clinicians as an adjunct to conventional pharmacological treatments. What are urgently required are rigorous evaluations of psychological therapies in asthma, on a par to the quality of pharmaceutical trials. From this evidence base, we can then determine which interventions are beneficial for our patients with asthma management and more specifically which psychological therapy is best suited for each patient

Efimov effect in quantum magnets

Physics is said to be universal when it emerges regardless of the underlying microscopic details. A prominent example is the Efimov effect, which predicts the emergence of an infinite tower of three-body bound states obeying discrete scale invariance when the particles interact resonantly. Because of its universality and peculiarity, the Efimov effect has been the subject of extensive research in chemical, atomic, nuclear and particle physics for decades. Here we employ an anisotropic Heisenberg model to show that collective excitations in quantum magnets (magnons) also exhibit the Efimov effect. We locate anisotropy-induced two-magnon resonances, compute binding energies of three magnons and find that they fit into the universal scaling law. We propose several approaches to experimentally realize the Efimov effect in quantum magnets, where the emergent Efimov states of magnons can be observed with commonly used spectroscopic measurements. Our study thus opens up new avenues for universal few-body physics in condensed matter systems.Comment: 7 pages, 5 figures; published versio

Galileons as Wess-Zumino Terms

We show that the galileons can be thought of as Wess-Zumino terms for the spontaneous breaking of space-time symmetries. Wess-Zumino terms are terms which are not captured by the coset construction for phenomenological Lagrangians with broken symmetries. Rather they are, in d space-time dimensions, d-form potentials for (d+1)-forms which are non-trivial co-cycles in Lie algebra cohomology of the full symmetry group relative to the unbroken symmetry group. We introduce the galileon algebras and construct the non-trivial (d+1)-form co-cycles, showing that the presence of galileons and multi-galileons in all dimensions is counted by the dimensions of particular Lie algebra cohomology groups. We also discuss the DBI and conformal galileons from this point of view, showing that they are not Wess-Zumino terms, with one exception in each case.Comment: 49 pages. v2 minor changes, version appearing in JHE

Impacts of climate change on plant diseases – opinions and trends

There has been a remarkable scientific output on the topic of how climate change is likely to affect plant diseases in the coming decades. This review addresses the need for review of this burgeoning literature by summarizing opinions of previous reviews and trends in recent studies on the impacts of climate change on plant health. Sudden Oak Death is used as an introductory case study: Californian forests could become even more susceptible to this emerging plant disease, if spring precipitations will be accompanied by warmer temperatures, although climate shifts may also affect the current synchronicity between host cambium activity and pathogen colonization rate. A summary of observed and predicted climate changes, as well as of direct effects of climate change on pathosystems, is provided. Prediction and management of climate change effects on plant health are complicated by indirect effects and the interactions with global change drivers. Uncertainty in models of plant disease development under climate change calls for a diversity of management strategies, from more participatory approaches to interdisciplinary science. Involvement of stakeholders and scientists from outside plant pathology shows the importance of trade-offs, for example in the land-sharing vs. sparing debate. Further research is needed on climate change and plant health in mountain, boreal, Mediterranean and tropical regions, with multiple climate change factors and scenarios (including our responses to it, e.g. the assisted migration of plants), in relation to endophytes, viruses and mycorrhiza, using long-term and large-scale datasets and considering various plant disease control methods